The correct option is Histamine.
Explanation
Basophils are a type of granulocyte (white blood cell) that constitute the smallest percentage (0.5-1 %) of the total leukocyte count. They play a significant role in the immune system, specifically in mediating inflammatory and allergic responses.
- Histamine is Correct: Basophils secrete inflammatory mediators including histamine, serotonin, and heparin. Histamine causes vasodilation and increases vascular permeability, which facilitates the inflammatory response.
- Antibodies is Incorrect: Antibodies (immunoglobulins) are produced by B-lymphocytes (specifically plasma cells) as part of the humoral immune response.
- Insulin is Incorrect: Insulin is a hormone involved in glucose metabolism, secreted by the beta cells of the Islets of Langerhans in the pancreas.
- Pepsin is Incorrect: Pepsin is a digestive enzyme responsible for breaking down proteins, secreted by the chief cells of the stomach lining.
Key Takeaway: Basophils are granulocytes involved in inflammatory reactions and are responsible for secreting histamine, serotonin, and heparin.